According to cloud computing, a plurality of virtual machines is deployed on a physical machine (an information processing device) in a data center by a virtualization infrastructure (hereinafter referred to as a hypervisor), and the deployed virtual machines construct a service system. A terminal device of a user who uses the service system accesses a virtual machine via a network to use the service system. The user deploys a needed virtual machine on a physical machine to construct a desired service system without procuring a physical machine on his/her own accord.
In cloud computing, when specific virtual machines are concentrated on a physical machine, it is possible to efficiently use hardware which is the physical machine and to save energy and resources.
For example, a hypervisor shares CPU resources with a plurality of virtual machines and changes CPU allocation from a virtual machine that is not using the CPU to a virtual machine that needs the CPU.
Moreover, as for memory resources, the hypervisor frees memory by moving not needed or not urgently needed data in the memory to an external storage device and changes allocation to a virtual machine that needs the memory.
In recent years, a hypervisor can create a memory overcommitment state in which memory equal to or greater than a memory capacity mounted on a physical machine is allocated to a virtual machine. For example, when a hypervisor allocates memory less than a memory capacity to a virtual machine, although the memory usage is relatively high, the CPU usage is low. Thus, from the perspective of the efficiency of a physical machine, it is requested to allocate memory to a virtual machine in a memory overcommitment state (for example, see Japanese Laid-open Patent Publication Nos. 7-28657, 2013-8322, and 2013-152513).